thermometer was used, reading to 

 about 0.1° F. , which could be 

 lowered to any desired depth for 

 a temperature reading. 



b. pH - these values were generally 

 measured electroraetrically , using 

 glass and saturated calomel elec- 

 trodes standardized against a 

 buffer solution. Colorimetric pH 

 determinations were made, using a 

 glass disc color comparator when 

 £in electrometric unit was judged 

 unreliable (following a trip over 

 rough roads) cind as a check on 

 the electrometric measurement. 



c. Dissolved oxygen - samples were 

 dosed at the time of collection 

 with reagents for the sodium 

 azide (Alsterberg) modification 

 of the Winkler method. The per- 

 centage of saturation was com- 

 puted using sea level saturation 

 values at the temperature of 

 sample collection. The percent- 

 age of saturation values were not 

 corrected for the altitude of 

 sample collection, i.e., baro- 

 metric pressure. 



d. Carbon dioxide - total carbon 

 dioxide was approximated by 

 adding 0.02 N NaOH to the phenol- 

 phthalein endpoint in a carefully 

 collected sample. 



e. Ammonia - sample was preserved 

 with 0.8 ml. of concentrated 

 ^2^^4 P^^ liter of sample at time 

 of collection. 



f. Alkalinity - total bicarbonate 

 and carbonate (if present) alka- 

 linity were determined by titra- 

 tion with 0.02 N H2Sq, against the 

 phenolphthalein and methyl or£Lnge 

 endpoints. 



g. Hardness - total hardness was 

 measured by titration using the 

 Schwarzenbach method. Carbonate 

 cUid non-carbonate hardness were 

 calculated, using the total 

 hardness — total alkalinity rela- 

 tionship. 



Determinations made on samples brought 

 back to the laboratory and the analytical 



procedures used were as follows: 



a. Color - "Aqua Tester" was used 

 to measure color by comparison 

 with a glass disc calibrated 

 against platinum-cobalt standards. 

 Excessive turbidity was removed 

 by centrifuging when necessary. 



b. Turbidity - A Hellige turbidime- 

 ter was used to measure low 

 turbidities. If turbidity values 

 exceeded 30, the sample was 

 diluted with distilled water. 

 The turbidimeter was calibrated 

 against a Jackson candle turbi- 

 dimeter. 



c. Conductivity - specific conduct- 

 ance was measured using a Wheat- 

 Stone bridge and a specific 

 conductance cell, calibrated 

 against a standard KCl solution. 

 Values were recorded in micro- 

 mhos/cm. , corrected to 25° C. 



d. Ammonia - determinations were 

 made by direct nessler ization in 

 nessler tubes, and color readings 

 were made by comparison with 

 permanent standards, or from an 

 electrophotometer calibrated 

 against permanent standards. Pre- 

 cipitated interfering substances 

 were removed by filtration or by 

 centrifugation. 



e. Sulfates - turbidimetric method 

 was used by precipitating the 

 sulfate ion with the barium ion 

 in acid solution. Turbidity 

 values, converted to p. p.m. of 

 sulfate ion, were read from a 

 Hellige turbidimeter calibrated 

 against standard sulfate solu- 

 tions. 



f. Total solids - 100 ml. of sample 

 was evaporated to dryness over a 

 water bath, dried for at least 

 one hour at 103° C. , and weighed. 

 Total solids and dissolved solids 

 will have about the same value 

 for nearly all stations where 

 turbidities were low. 



Samples for element analysis were 

 periodically sent to a commercial labora- 

 tory set up for this type of analytical 



24 



